Stabilized aqueous amide antimicrobial composition

Abstract

Aqueous antimicrobial compositions which comprise a halogenated amide antimicrobial, such as 2,2-dibromonitrilopropionamide, a water miscible organic solvent such as a straight chain polyalkylene glycol (e.g., polyethylene glycol 200) or an ether thereof (e.g., a mono- or di- lower alkyl and/or phenyl ether) and water are stabilized against decomposition of the halogenated amide antimicrobial by the addition of a cyclic ether stabilizer such as tetrahydrofuran, tetrahydropyran, 1,4-dioxane, sym-trioxane, N-methyl morpholine, etc. The compositions, so stabilized, exhibit reduced rates of decomposition of the halogenated amide antimicrobial relative to the corresponding non-stabilized aqueous compositions.

What is claimed is: 
     
       1. An aqueous antimicrobial composition having a pH of from about 2 to about 5 and comprising: (a) an alpha-halogenated amide antimicrobial compound of the formula: ##STR4## wherein: X is hydrogen, halogen or a cyano radical; each R group is independently hydrogen, a monovalent saturated hydrocarbon radical or an inertly substituted monovalent saturated hydrocarbon radical or the two R groups are jointly a divalent saturated hydrocarbon radical or an inertly substituted divalent saturated hydrocarbon radical which, taken with the adjacent nitrogen atom, forms a heterocyclic ring having from 4 to about 10 ring members; and   R 1  is a cyano radical or an amido radical of the formula: ##STR5## wherein R is as hereinbefore defined; (b) a water-miscible organic solvent in an amount sufficient to dissolve the halogenated amide antimicrobial, said solvent being a normally liquid polyalkylene glycol of the ethylene, trimethylene or tetramethylene series or a mono- or di-saturated hydrocarbyl ether thereof;   (c) water; and   (d) a stabilizing amount of a 5- or 6-membered saturated cyclic ether or an inertly substituted 5- or 6-membered saturated cyclic ether, said stabilizing amount being an amount sufficient to measurably reduce the decomposition of the halogenated amide antimicrobial in the aqueous composition and said cyclic ether corresponding to the formula: ##STR6##  wherein Q represents divalent organic radical of the formula --C(R 2 ) 2  --C(R 2 ) 2  --, --C(R 2 ) 2  --O--, --C(R 2 ) 2  --C(R 2 ) 2  --C(R 2 ) 2  --, --C(R 2 ) 2  --O--C(R 2 ) 2  --, --C(R 2 ) 2  --C(R 2 ) 2  --O--, --O--C(R 2 ) 2  --O--, or --C(R 2 ) 2  --N(R 2 )--C(R 2 ) 2  --and wherein each R 2  is individually hydrogen or a monovalent saturated hydrocarbon radical containing from 1 to about 8 carbon atoms.     
     
     
       2. The composition of claim 1 wherein the polyalkylene glycol or ether thereof has a weight average molecular weight of from about 75 to about 1000. 
     
     
       3. The composition of claim 1 wherein, in the antimicrobial compound, X is hydrogen, bromine or chlorine;   each R group is independently hydrogen, a monovalent saturated hydrocarbon radical or an inertly substituted monovalent saturated hydrocarbon radical; and   R 1  is a cyano radical.   
     
     
       4. The composition of claim 1 wherein, in the antimicrobial compound: X is hydrogen, chlorine or bromine and   R 1  is a cyano radical.   
     
     
       5. The composition of claim 1 wherein the antimicrobial compound is 2,2-dibromo-3-nitrilopropionamide. 
     
     
       6. The composition of claim 1 wherein each R 2  substituent of the cyclic ether is individually hydrogen, an alkyl group containing from 1 to about 6 carbon atoms, a phenyl radical or a benzyl radical. 
     
     
       7. The composition of claim 1 wherein the cyclic ether is tetrahydrofuran, 1,4-dioxane, 1,3,5-trioxane or N-methyl morpholine. 
     
     
       8. The composition of claim 7 wherein the water-soluble organic solvent is polyethylene glycol, having a weight average molecular weight of about 200; the antimicrobial compound is 2,2-dibromo-3-nitrilopropionamide; and the pH of the aqueous antimicrobial composition is from about 3 to about 4. 
     
     
       9. The composition of claim 1 wherein: (a) the antimicrobial compound constitutes from about 1 to about 25 weight percent of the total composition;   (b) the water constitutes from about 20 to about 60 weight percent of the total composition;   (c) the water miscible organic solvent constitutes from about 25 to about 75 weight percent of the total composition; and   (d) the cyclic ether constitutes from about 0.1 to about 5 weight percent of the total composition.   
     
     
       10. A process for preparing the aqueous antimicrobial composition of claim 1 which process comprises the steps of: (a) preparing the alpha-halogenated amide antimicrobial by the acid catalyzed reaction of the corresponding nonhalogenated amide with halogen in aqueous solution, at a temperature of less than about 40° C., and in the presence of hydrogen halide at a concentration which is less than about 20 weight percent on a total weight basis but which is sufficient to catalyze the reaction;   (b) dissolving the resulting aqueous reaction mixture in the water miscible organic solvent;   (c) adding to the reaction mixture of step (a), or to the water miscible organic solvent solution of step (b), a stabilizing amount of the cyclic ether stabilizer; and   (d) adjusting the pH of the product of step (a), (b) or (c) such that the aqueous antimicrobial composition has a pH of from about 2 to about 5.   
     
     
       11. The process of claim 10 in which the pH adjustment is such that the aqueous antimicrobial composition has a pH of from about 3 to about 4. 
     
     
       12. The process of claim 10 wherein the halogenated amide antimicrobial is 2,2-dibromo-3-nitrilopropionamide and the halogen is bromine; the water-miscible organic solvent is polyethylene glycol, or a lower alkyl ether thereof, having a weight average molecular weight of about 200; and the cyclic ether is tetrahydrofuran, 1,4-dioxane, 1,3,5-trioxane or N-methyl morpholine. 
     
     
       13. The process of claim 10 wherein a water-soluble bromate is introduced to the aqueous reaction medium during preparation of the halogenated amide antimicrobial; and the pH of the aqueous reaction mixture is adjusted to a value of from about 5 to about 7 by the addition of an alkali metal, or an alkaline earth metal, carbonate or bicarbonate to such reaction mixture following the preparation of the halogenated amide and prior to the dissolution of such reaction mixture in the organic solvent. 
     
     
       14. An aqueous antimicrobial composition having a pH of from about 2 to about 5 and comprising, based upon the total weight of such composition: (a) from about 1 to about 25 weight percent of a halogenated amide antimicrobial of the formula: ##STR7##  wherein X is hydrogen, chlorine or bromine and each R is independently hydrogen, an alkyl group of from 1 to about 6 carbon atoms or phenyl;   (b) from about 5 to about 90 weight percent of water;   (c) from about 5 to about 90 weight percent of a water-miscible organic solvent which is selected from the group consisting of polyethylene glycols, trimethylene glycols, tetramethylene glycols and the mono- and di- phenyl or C 1  to about C 6  alkyl ethers thereof and which has a weight average molecular weight of from about 75 to about 1000; and   (d) a stabilizing amount, in the range of from about 0.05 to about 10 weight percent, of a cyclic ether of the formula: ##STR8##  wherein Q represents divalent organic radical of the formula --C(R 2 ) 2  --C(R 2 ) 2  --, --C(R 2 ) 2  --O--, --C(R 2 ) 2  --C(R 2 ) 2  --C(R 2 ) 2  --, --C(R 2 ) 2  --O--C(R 2 ) 2  --, --C(R 2 ) 2  --C(R 2 ) 2  --O--, --O--C(R 2 ) 2  --O--, or --C(R 2 ) 2  --N(R 2 )--C(R 2 ) 2  --and wherein each R 2  is individually hydrogen, an alkyl group of from 1 to about 6 carbon atoms, phenyl or benzyl.   
     
     
       15. The composition of claim 14 wherein the halogenated amide antimicrobial is 2,2-dibromo-3-nitrilopropionamide. 
     
     
       16. The composition of claim 15 wherein the water-miscible organic solvent is polyethylene glycol having a weight average molecular weight of from about 175 to about 250. 
     
     
       17. The composition of claim 15 wherein the water-miscible organic solvent is polyethylene glycol 200. 
     
     
       18. The composition of claim 16 wherein the cyclic ether is tetrahydrofuran, 1,4-dioxane, 1,3,5-trioxane or N-methyl morpholine. 
     
     
       19. A process for preparing the aqueous antimicrobial composition of claim 18 which process comprises the steps of: (a) preparing the 2,2-dibromo-3-nitrilopropionamide by the reaction of cyanoacetamide with bromine in aqueous solution (1) at a temperature of less than about 40° C., (2) in the presence of HBr at a concentration which is less than about 20 weight percent on a total weight basis but which is sufficient to catalyze the reaction and (3) in the presence of an alkali metal or an alkaline earth metal bromate;   (b) dissolving the resulting aqueous reaction mixture in the polyethylene glycol having a weight average molecular weight of from about 175 to about 250;   (c) adding to the reaction mixture of step (a) or to the solution thereof of step (b) a stabilizing amount of tetrahydrofuran, 1,4-dioxane, 1,3,5-trioxane or N-methyl morpholine; and   (d) adjusting the pH of the product of step (a), (b) or (c) such that the aqueous antimicrobial composition has a pH of from about 2 to about 5.